The present invention relates to the manner in which a vehicle navigation system communicates a calculated route to a driver. More specifically, the present invention relates to the timing of warning prompts which alert the driver to upcoming maneuvers.
Vehicle navigations systems employ a variety of methods for communicating a route to a driver. One method employs warning chimes to alert the driver to an upcoming maneuver. Another employs a series of voice prompts. The timing of these chimes or voice prompts are crucial to effective route guidance. If a prompt is delayed, the driver may not be able to execute the maneuver in a safe and orderly manner. If a prompt is issued too early and a significant amount of time elapses before the vehicle arrives at the maneuver location, the driver may not be properly alert.
Currently available vehicle navigation systems which have warning chimes or voice guidance typically employ a fixed distance at which the driver is warned of an upcoming maneuver. That is, once the vehicle is determined to be within a particular distance of the geographic location at which the maneuver is to be executed, the system issues the warning chime or the voice guidance prompt. Unfortunately, this method does not account for the often widely varying characteristics of the environment in which the vehicle is operating. For example, if the fixed warning distance is set to provide adequate notice to the driver in a freeway environment where the speed limit is 65 miles per hour, it will likely be too long for a residential area where the speed limit is typically 25 miles per hour.
Moreover, a fixed warning distance may cause confusion by encompassing more than one junction at which similar maneuvers may be executed. This will almost certainly be the case where the fixed warning distance is set relative to a freeway environment. Because such a warning distance would be relatively long, it would likely encompass more than one intersection in a different environment where the average vehicle speed is considerably less such as, for example, a residential environment. Such confusion is unacceptable if a vehicle navigation system is to adequately guide the driver along a calculated route.
It is therefore evident that a more flexible approach is needed for communicating warnings of impending maneuvers to the user of a vehicle navigation system.